‘Traditionally’ boys always wore black or green undies under the kilt. The tradition I assume dates from nineteenth century, before that, almost certainly too poor for anything other than a rag both as kilt and under garment.

Yeah buddy! I couldn’t help but zoom in on his adorable face I love the boy wearing kilts. Why take off underwear and let the little birdie be seen? That would ruin the fun at the event he was competing in, and would have lead to his disqualification for improper dress and most serious, indecent exposure.